As an example of a tumor tracking irradiation apparatus capable of automatically calculating a position of a tumor moving around in a trunk of a body in real time and ensuring substantially necessary accuracy without depending on absolute accuracy of a mechanical system, PTL 1 discloses a tumor tracking irradiation apparatus including: an imaging device that simultaneously images a fiducial marker embedded in the vicinity of the tumor from the first and second directions to obtain first and second captured images; an image input recognition processing unit that executes template matching by normalized cross-correlation in which a template image of the fiducial marker, which is registered in advance, is applied to digitized first and second captured images, at a real time level of a predetermined frame rate and calculates first and second two-dimensional coordinates of the fiducial marker based on first and second image transformation matrices; a central processing unit that calculates three-dimensional coordinates of the fiducial marker based on the calculated first and second two-dimensional coordinates; and an irradiation control unit that controls treatment beam irradiation of linac based on the calculated three-dimensional coordinates of the fiducial marker.